High throwpower, or the ability of an electrodepositable coating to coat interior or recessed surfaces to provide corrosion protection in difficult to coat areas, is a desirable trait in electrodepositable coatings. During electrodeposition, exterior surfaces and surfaces closer to the cathode are coated first, and the coating thickness at these locations continues to increase as surfaces further from the cathode are subsequently coated. As a result, in order for a standard electrodepositable coating to achieve minimum targets on interior surfaces and/or surfaces further from the cathode, film thickness on exterior surfaces and surfaces closer to the cathode may significantly exceed target levels. Electrodepositable coatings with higher throwpower result in a coating with a more uniform film thickness over the surface of the substrate. Using a superior throwpower electrocoat reduces paint consumption, the number of partial or uncoated parts, and the reprocessing associated with them.
Additionally, cationic electrocoats which use cyclic guanidine in the amination of epoxy resins cure effectively with blocked isocyanates in the absence of other metal catalysts. However, coating compositions that include cyclic guanidine deposit on substrate poorly and conventional methods of altering throwpower, such as by increasing voltage, increasing current density, and/or increasing the time in which electrodeposition takes place do not ameliorate the deficiencies.
Accordingly, there is a need for a cyclic guanidine-containing coating composition that is efficiently and adequately deposited on a substrate.